A batch type vertical hot-wall heat treating apparatus is widely used in heat treatment processes such as oxidizing, diffusion or annealing process applied to the wafer at comparatively high temperatures in IC manufacturing methods.
This batch type vertical hot-wall heat treating apparatus (hereafter called, heat treating apparatus) includes a process tube installed vertically to form the processing chamber where the wafers are carried in; a heater unit for heating the processing chamber outside the process tube; a boat loaded into and out of the processing chamber, supporting multiple wafers on multiple stage support grooves; and a standby chamber for keeping the boat to be loaded into or out of the processing chamber in a stand-by state.
After the multiple wafers are charged (wafer charging) in the boat in the standby chamber, they are loaded (boat loading) from the standby chamber into the preheated processing chamber. The wafers are then subjected to the desired heat treatment because the processing chamber is heated to the specified heat treating temperature by the heater unit.
The boat in conventional heat treating apparatus of this type, includes a pair of upper and lower edge plates, three piece support members installed for example vertically in between both edge plates, and multiple support grooves formed at equidistant intervals longitudinally on the three piece support members and formed with openings mutually facing each other. The multiple wafers are supported horizontally while arrayed with their centers mutually aligned because they are inserted in the support grooves of the three piece support members.
However, boats with this type of structure possess the following problems. The entire weight of the wafer is supported only by the three support grooves so that when a thermal stress is suddenly applied to the wafer, a crystallizing flaw (slip) then occurs due to its own weight stress and the tensile stress on the contact surface between the wafer and support grooves, and warping occurs on the wafer.
The wafer holder in patent document 1 was disclosed as technology for resolving the problem.
This wafer holder was formed from silicon carbide (SiC) in a circular ring shape for supporting the periphery of the wafer. This wafer holder dispersed and supported the total weight of the wafer along the entire circumference and in this way reduced the gravitational force applied to support points on the wafer contacting the wafer holder and also prevented wafer slip and damage as well as wafer warping.
Patent document 1: Japanese Patent Non-examined Publication No. 7-45691